Almost all mobile device users have had the experience of being in a noisy environment such as a train station, airport or public gathering and being unable to hear a phone call. An additional experience that most mobile device users have had is being unable to hear public announcements in a noisy environment. In some cases, public announcements become garbled due to audio equipment issues, surrounding ambient noise, or even the user's hearing. Because of these issues, public announcements in train stations and airports are sometimes missed by the intended audience, which can cause passengers to miss their train or flight. In other public venues, a safety hazard may occur if people in the crowd do not hear emergency messages that are being broadcast.
Also at railway track crossings, mobile device users that are listening to entertainment audio such as songs or radio broadcasts using a headset accessory often become unaware of their surroundings and may not keep in mind that a train approaching, creating an extremely dangerous situation.